[board] Copy fen.rs here from the position crate
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board/src/fen.rs
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330
board/src/fen.rs
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// Eryn Wells <eryn@erynwells.me>
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use crate::{Board, Builder, Castle, EnPassant};
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use chessfriend_core::{
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coordinates::ParseSquareError, piece, Color, File, Piece, PlacedPiece, Rank, Square,
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};
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use std::fmt::Write;
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#[macro_export]
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macro_rules! fen {
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($fen_string:literal) => {
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Board::from_fen_str($fen_string)
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};
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}
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#[derive(Clone, Debug, Eq, PartialEq)]
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pub enum ToFenStrError {
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FmtError(std::fmt::Error),
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}
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#[derive(Clone, Debug, Eq, PartialEq)]
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pub enum FromFenStrError {
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MissingField(Field),
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MissingPlacement,
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InvalidValue,
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ParseIntError(std::num::ParseIntError),
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ParseSquareError(ParseSquareError),
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}
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#[derive(Clone, Debug, Eq, PartialEq)]
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pub enum Field {
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Placements,
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PlayerToMove,
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CastlingRights,
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EnPassantSquare,
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HalfMoveClock,
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FullMoveCounter,
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}
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pub trait ToFenStr {
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type Error;
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/// Create a FEN string from `Self`.
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///
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/// # Errors
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///
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///
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fn to_fen_str(&self) -> Result<String, Self::Error>;
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}
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pub trait FromFenStr: Sized {
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type Error;
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/// Create a `Self` from a FEN string.
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///
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/// # Errors
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///
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///
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fn from_fen_str(string: &str) -> Result<Self, Self::Error>;
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}
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impl ToFenStr for Board {
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type Error = ToFenStrError;
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fn to_fen_str(&self) -> Result<String, Self::Error> {
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let mut fen_string = String::new();
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let mut empty_squares: u8 = 0;
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for rank in Rank::ALL.into_iter().rev() {
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for file in File::ALL {
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let square = Square::from_file_rank(file, rank);
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match self.piece_on_square(square) {
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Some(piece) => {
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if empty_squares > 0 {
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write!(fen_string, "{empty_squares}")
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.map_err(ToFenStrError::FmtError)?;
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empty_squares = 0;
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}
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write!(fen_string, "{}", piece.to_fen_str()?)
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.map_err(ToFenStrError::FmtError)?;
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}
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None => empty_squares += 1,
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}
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}
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if empty_squares > 0 {
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write!(fen_string, "{empty_squares}").map_err(ToFenStrError::FmtError)?;
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empty_squares = 0;
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}
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if rank != Rank::ONE {
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write!(fen_string, "/").map_err(ToFenStrError::FmtError)?;
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}
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}
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write!(fen_string, " {}", self.player_to_move().to_fen_str()?)
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.map_err(ToFenStrError::FmtError)?;
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let castling = [
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(Color::White, Castle::KingSide),
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(Color::White, Castle::QueenSide),
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(Color::Black, Castle::KingSide),
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(Color::Black, Castle::QueenSide),
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]
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.map(|(color, castle)| {
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let can_castle = self.player_has_right_to_castle(color, castle);
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if !can_castle {
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return "";
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}
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match (color, castle) {
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(Color::White, Castle::KingSide) => "K",
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(Color::White, Castle::QueenSide) => "Q",
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(Color::Black, Castle::KingSide) => "k",
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(Color::Black, Castle::QueenSide) => "q",
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}
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})
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.concat();
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write!(
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fen_string,
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" {}",
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if castling.is_empty() { "-" } else { &castling }
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)
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.map_err(ToFenStrError::FmtError)?;
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write!(
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fen_string,
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" {}",
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self.en_passant()
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.map_or("-".to_string(), |ep| ep.target_square().to_string())
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)
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.map_err(ToFenStrError::FmtError)?;
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write!(fen_string, " {}", self.ply_counter()).map_err(ToFenStrError::FmtError)?;
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write!(fen_string, " {}", self.move_number()).map_err(ToFenStrError::FmtError)?;
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Ok(fen_string)
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}
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}
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impl ToFenStr for Color {
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type Error = ToFenStrError;
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fn to_fen_str(&self) -> Result<String, Self::Error> {
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match self {
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Color::White => Ok("w".to_string()),
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Color::Black => Ok("b".to_string()),
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}
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}
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}
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impl ToFenStr for Piece {
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type Error = ToFenStrError;
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fn to_fen_str(&self) -> Result<String, Self::Error> {
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let ascii: char = self.to_ascii();
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Ok(String::from(match self.color() {
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Color::White => ascii.to_ascii_uppercase(),
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Color::Black => ascii.to_ascii_lowercase(),
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}))
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}
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}
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impl ToFenStr for PlacedPiece {
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type Error = ToFenStrError;
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fn to_fen_str(&self) -> Result<String, Self::Error> {
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self.piece().to_fen_str()
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}
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}
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impl FromFenStr for Board {
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type Error = FromFenStrError;
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fn from_fen_str(string: &str) -> Result<Self, Self::Error> {
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let mut builder = Builder::default();
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let mut fields = string.split(' ');
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let placements = fields
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.next()
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.ok_or(FromFenStrError::MissingField(Field::Placements))?;
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let ranks = placements.split('/');
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for (rank, pieces) in Rank::ALL.iter().rev().zip(ranks) {
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let mut files = File::ALL.iter();
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for ch in pieces.chars() {
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if let Some(skip) = ch.to_digit(10) {
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// TODO: Use advance_by() when it's available.
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for _ in 0..skip {
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files.next();
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}
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continue;
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}
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let file = files.next().ok_or(FromFenStrError::MissingPlacement)?;
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let piece = Piece::from_fen_str(&ch.to_string())?;
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builder.place_piece(PlacedPiece::new(
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piece,
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Square::from_file_rank(*file, *rank),
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));
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}
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debug_assert_eq!(files.next(), None);
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}
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let player_to_move = Color::from_fen_str(
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fields
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.next()
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.ok_or(FromFenStrError::MissingField(Field::PlayerToMove))?,
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)?;
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builder.to_move(player_to_move);
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let castling_rights = fields
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.next()
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.ok_or(FromFenStrError::MissingField(Field::CastlingRights))?;
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if castling_rights == "-" {
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builder.no_castling_rights();
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} else {
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for ch in castling_rights.chars() {
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match ch {
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'K' => builder.player_can_castle(Color::White, Castle::KingSide),
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'Q' => builder.player_can_castle(Color::White, Castle::QueenSide),
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'k' => builder.player_can_castle(Color::Black, Castle::KingSide),
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'q' => builder.player_can_castle(Color::Black, Castle::QueenSide),
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_ => return Err(FromFenStrError::InvalidValue),
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};
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}
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}
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let en_passant_square = fields
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.next()
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.ok_or(FromFenStrError::MissingField(Field::EnPassantSquare))?;
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if en_passant_square != "-" {
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let square = Square::from_algebraic_str(en_passant_square)
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.map_err(FromFenStrError::ParseSquareError)?;
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builder.en_passant(Some(EnPassant::from_target_square(square).unwrap()));
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}
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let half_move_clock = fields
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.next()
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.ok_or(FromFenStrError::MissingField(Field::HalfMoveClock))?;
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let half_move_clock: u16 = half_move_clock
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.parse()
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.map_err(FromFenStrError::ParseIntError)?;
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builder.ply_counter(half_move_clock);
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let full_move_counter = fields
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.next()
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.ok_or(FromFenStrError::MissingField(Field::FullMoveCounter))?;
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let full_move_counter: u16 = full_move_counter
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.parse()
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.map_err(FromFenStrError::ParseIntError)?;
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builder.move_number(full_move_counter);
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debug_assert_eq!(fields.next(), None);
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Ok(builder.build())
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}
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}
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impl FromFenStr for Color {
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type Error = FromFenStrError;
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fn from_fen_str(string: &str) -> Result<Self, Self::Error> {
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if string.len() != 1 {
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return Err(FromFenStrError::InvalidValue);
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}
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match string.chars().take(1).next().unwrap() {
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'w' => Ok(Color::White),
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'b' => Ok(Color::Black),
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_ => Err(FromFenStrError::InvalidValue),
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}
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}
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}
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impl FromFenStr for Piece {
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type Error = FromFenStrError;
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fn from_fen_str(string: &str) -> Result<Self, Self::Error> {
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if string.len() != 1 {
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return Err(FromFenStrError::InvalidValue);
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}
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match string.chars().take(1).next().unwrap() {
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'P' => Ok(piece!(White Pawn)),
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'N' => Ok(piece!(White Knight)),
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'B' => Ok(piece!(White Bishop)),
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'R' => Ok(piece!(White Rook)),
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'Q' => Ok(piece!(White Queen)),
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'K' => Ok(piece!(White King)),
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'p' => Ok(piece!(Black Pawn)),
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'n' => Ok(piece!(Black Knight)),
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'b' => Ok(piece!(Black Bishop)),
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'r' => Ok(piece!(Black Rook)),
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'q' => Ok(piece!(Black Queen)),
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'k' => Ok(piece!(Black King)),
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_ => Err(FromFenStrError::InvalidValue),
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}
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use crate::test_board;
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#[test]
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fn starting_position() {
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let pos = test_board!(starting);
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assert_eq!(
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pos.to_fen_str(),
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Ok(String::from(
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"rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"
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))
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);
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}
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#[test]
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fn from_starting_fen() {
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let board = fen!("rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1").unwrap();
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let expected = Board::starting();
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assert_eq!(board, expected, "{board:#?}\n{expected:#?}");
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}
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}
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